438 PROCEEDINGS OF THE AMERICAN ACADEMY. 



To make an alkaline solution, one per cent of potassic hydrate was 

 added to sea water, with the result that a somewhat milky precipitate 

 was formed. The filtrate from this mixture had a strongly alkaline 

 taste, but it did not call forth any response when it was applied either 

 to the tail or to the middle of amphioxus. At the anterior end it 

 caused the animal to dart backward vigorously. 



For a bitter material picric acid was used. About a "^ solution 

 is very near saturation in sea water. To this solution, when applied 

 to the tail, middle, and anterior end, amphioxus reacted with charac- 

 teristic locomotion. All three regions were also stimulated by a ^3^ 

 solution, but locomotion usually did not result. At yffg occasional 

 slight reactions were obtained, but only when the solution was applied 

 to the anterior end, the tail and middle being apparently insensitive 

 to this strength. 



When a ten per cent solution of cane sugar in sea water was dis- 

 charged freely over the anterior end, the middle, or the tail of 

 amphioxus, no reaction of any kind was given. 



No reactions were observed when the surface of the animal was 

 bathed with sea water containing the following substances in solution : 

 ether, chloroform, turpentine, oil of bei'gamot, and oil of rosemary. 

 However, when any of these materials in a pure state was applied 

 directly to the skin of amphioxus, a vigorous locomotor response was 

 elicited, as Nagel ('94'', p. 58) had previously found for chloroform and 

 oil of rosemary. 



A one per cent solution of alcohol in sea water called forth no 

 response when applied to the anterior end, the middle, or the tail of 

 amphioxus. A five per cent solution stimulated the anterior end and 

 tail but not the middle, and a ten per cent solution stimulated all 

 three parts. 



Not only are many chemical solutions stimulating to amphioxus, 

 but fresh water is likewise. When animals were dropped into sea 

 water to which had been added one- fourth fresh water, the animals 

 were observed to swim for a time more vigorously than in pure sea 

 water. When the sea water was diluted by an equal volume or more 

 of fresh water, the amphioxus swam most vigorously, and in very 

 dilute sea water or in fresh water they quickly died, as already ob- 

 served by Bert ('69, p. 21) and by Johnston (:05, p. 115). These 

 various mixtures were also locally stimulating. The mixture of one- 

 fourth fresh water and three-fourths sea water induced a slight back- 

 ward movement when applied to the anterior end, but apparently 

 stimulated no other part of the body. All mixtures containing more 

 than one-fourth fresh water stimulated both the anterior end and the 



